In most cases, the scaling of RDS Capacity Units (RCUs) for a serverless ApsaraDB RDS for PostgreSQL instance immediately takes effect and does not affect workloads. In some extreme cases, a transient connection may occur during RCU scaling. ApsaraDB RDS for PostgreSQL allows you to configure a scaling policy to specify whether to forcefully scale RCUs of a serverless RDS instance in extreme cases.
The default scaling policy of a serverless RDS instance is Do Not Execute Forcefully. If the RCU scaling of the serverless RDS instance may cause a transient connection, the system ignores the RCU scaling request. This policy ensures instance availability but may adversely affect instance performance.
You can manually change the scaling policy to Execute Forcefully. If the system receives the RCU scaling request, the system forcefully scales RCUs regardless of the instance status or transient connections. This policy may cause a transient connection that lasts approximately 1 minute during the RCU scaling of a serverless RDS instance. This policy ensures instance performance but cannot ensure instance availability in extreme cases.
Transient connections are countermeasures in emergency cases. The probability of transient connections is extremely low.
The operations in this topic apply only to serverless RDS instances. Make sure that the billing method of your RDS instance is serverless.
The default scaling policy of a serverless RDS instance is Do Not Execute Forcefully. If the RCU scaling of the serverless RDS instance may cause a transient connection, the system ignores the RCU scaling request, and instance performance is adversely affected.
If you manually change the scaling policy to Execute Forcefully, transient connections may occur in extreme cases and affect your workloads.
If no serverless RDS instances are created, you can configure the Scaling Policy parameter when you create a serverless RDS instance. For more information, see Create a serverless ApsaraDB RDS for PostgreSQL instance.
If a serverless RDS instance is created, you can perform the following steps to modify the Scaling Policy parameter:
- Go to the Instances page. In the top navigation bar, select the region in which the RDS instance resides. Then, find the RDS instance and click the ID of the instance.
In the Configuration Information section, click Modify Scaling Settings.
Click Advanced Settings. In the Scaling Policy drop-down list, select Do Not Execute Forcefully or Execute Forcefully based on your business requirements. Then, click OK in the lower part of the page.
You can call the ModifyDBInstanceSpec operation to modify the scaling policy of a serverless RDS instance. The following table describes the parameters.
The ID of the serverless instance for which you want to change the scaling range of RCUs.
The billing method of the serverless instance. Set the value to Serverless.
The specification change type of the instance. Set the value to Serverless.
Specifies whether to forcefully scale RCUs for the serverless RDS instance. Valid values: